Tubular WaterOne way to envision water pulled into and up a capillary tube is to use a suspension bridge model. The column of water is suspended against gravity by its adherence to the walls of the tube. Cohesive force keep all the water molecules together. Capillary movement is greater as tube diameter decreases. Extremely small diameter tubes, pores, or spaces can attract water and move it a relatively long way. Capillary movement is responsible for within- and between-cell water movement in trees, and small pore space movements in soils. Cell wall spaces are extremely small (interfibral) and can slowly wick-up water. The water conducting tissues of trees (xylem), does not utilize capillary movement for water transport. If xylem were open at its top, a maximum capillary rise of 2-3 feet could be obtained. Xylem transport is by mass movement of water not capillary action. Capillary movement is a matter of inches, not dragging water to the top of a 300 feet tall tree. Capillary movement components can be seen where liquid water touches the side of a glass. The water does not abruptly stop at the glass interface, but is drawn slightly up the sides of the glass. This raised rim is called a "meniscus." The meniscus is the visible sign of adhesive forces between the glass and water pulled up the side of the glass. The smaller the diameter of the glass, the greater the adhesive forces pulling-up on the water column and the less mass suspended behind.Tiny BubblesGas bubble formation in water columns is called cavitation. As temperatures rise and tension in the water column increases, more gases will fall out of solution and form small bubbles. These tiny bubbles may gather and coalesce, "snapping" the water column. As temperatures decrease, water can hold more dissolved gasses until it freezes. Freezing allows gases to escape and potentially cavitates water conducting tissue when thawed. Trees do have some limited means to reduce these cavitation faults.On The MoveWater movement and transportation of materials is essential to tree life. The three major forms of transport are driven by diffusion, mass flow, and osmosis forces. Diffusion – Diffusion operates over cell distances. Diffusion is the movement of dissolved materials from high concentrations areas to low concentration areas. Diffusion can move a dissolved molecule in water across a cell in a few seconds. Diffusion does not operate biologically over larger distances. It would take decades to diffuse a molecule across a distance of one yard / one meter.Mass Flow – Most movements we visualize are due to the mass flow of materials caused by pressure differences. Wind, gravity, and transpiration forces initiate and sustain small differences in pressure. These small differences drive water and its dissolved load of materials in many different directions. Because pressure is the driving force in mass flow, (not concentration differences as in diffusion), the size of the conduit is critical to flow rates. If the radius of the conduit is doubled, volume flow increases to the fourth power of the size increase (double conduit radius and flow rate increases by 16 times — 24). Osmosis – Osmosis is the movement of water across a membrane. Membranes in living tree cells separate and protect different processes and cellular parts. Membranes act as selective filters, preventing materials with large hydration spheres or layers from passing through. Small, uncharged materials may pass freely. The driving force to move materials in osmosis is a combination of pressure and concentration forces called a "water potential gradient."

by Dr. Kim D. CoderDaniel B. Warnell School of Forest ResourcesUniversity of Georgia6/99

Death is natures way of telling us to slow down.

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As far as I can work out the presently accepted way water gets up a tree is:

The xylem are full of water from the beginning, as each year they grow up from the roots and are full of water from the start. This column of water is essentially hanging from the top of the column, and is stable (despite being under considerable negative pressure) because the xylem is so small and covered with hydrophillic substances so cavitation is difficult as I described above (this is known as the cohesiveness of water).

Now the tissue around the xylem have more sugar and other salts dissolved in them than are in contents of the xylem so they suck water across the cell membranes surrounding the xylem by osmosis. You are right to point out that osmosis is a slow process, but this is happening over the whole area of the tree so it adds up.

Because the water is cohesive if you pull on the top the whole column moves up like a piece of string so it sucks water in at the bottom.

The water in the cells evaporates concentrating the salts and sugars in them, and allowing them to draw more water in by osmosis. So the energy to power the whole process comes from the sun evaporating water in the leaves.

Dave, lets not forget the limit which suction can work under normal atmospheric pressure in physics. I.E. a pump/suction placed above a water source has a ceiling. Above 10 metres, the pump fails to work, and the water level remains at 10 metres, and the space above the 10 metres is vacuum, the limit was discovered by Galileo, while asked to work out why water at 40 feet below the surface could not be drawn up by a pump. Cavitations do occur and can be heard as cracking noises in a tree using a stethoscope.

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As I mentioned earlier it is possible to get water below ther pressure it should cavitate and therefore be able to suck it up more than 10metres, (in the same way as you can super heat water) especially if you are in a very thin tube covered in hydrophillic substances (or a xylem as it is otherwise known). In fact looking at the web (and from a conversation we had in Brixham once) you have syphoned water 24m vertically using quite a large tube, so it must be possible to do better with this using a smaller tube.

Yes cavitation does happen, especially in drought conditions, but surely that shows that the water in the xylae is under tension and therefore unstable, so is evidence for the standard theory. There are a lot of xylae in a tree and it will be ok as long as the tree is growing the xylae faster than they are breaking due to cavitation.

Dave, the water at Brixham was not siphoned, as you well know a siphon will not work at those heights. In fact, to prove it was not a siphon that was taking place, I lowered one of the bottles in my experiment to see if siphon would occur, and because there was no saline solution at the centre of the loop of tubing no circulation took place, therefore disproving that we were looking at a siphon.

We can agree now on the fact that cavitations are known to occur. I believe that when a cavity occurs, the pressure changes reverse to a positive downward force, which has a direct influence on fluids in the rest of the tree, forcing the fluids in nearby tubes to rise higher and repair the cavitations, therefore enabling the bulk flow to continue.

Having said that, I am intrigued as to where and when we met, did you attend the demonstration in 1994?

Andrew

Death is natures way of telling us to slow down.

« Last Edit: 27/04/2005 16:49:40 by Andrew K Fletcher »

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Hm, yes... I agree not exactly a siphon in the traditional sense... but i can't see why that matters. Whatever the source of the upward "pull" on the water at the top of the left hand column, it's still just a pull at that point, as would be the pull due to transfer of the water across a cell membrane by osmosis. I really can't see where this tells us anything new.

RosyThanks for agreeing with me on the non-siphon effect.Strange that you cant find anything new in this? The flow rates observed within this simple paradigm parallel any observed rates in trees or plants, if not exceed them with ease. That being because of the obvious fluid friction within a tree or plant and the lesser degree of friction in the tubular models.

One should not jump to the conclusion that current understanding of osmosis is comparative to the efficacy of the new paradigm, without first testing the simple tubular experiments for oneself.

Andrew

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You had at in the experiment a loop of tube filled with water with a height difference from the top to the bottom of more than 10m? So you have prooved that a column of water more than 10m high is stable, so why shouldn't a xylem be able to do the same thing? Especially as it has had 200million years to optmise this process.

You are right what you were doing (injecting denser fluid near the top of the tube on one arm of a syphon loop) is not conventional syphoning, you are making one arm of the syphon heavier by using a higher density fluid rather than by using a lengthened arm, but if this works then a syphon will work.

If the water column has not cavitated there is no reason why it shouldn't syphon - the reason why it is often said that you can't syphon over 34 feet is that the fluid will have a tendancy to cavitate. How far did you lower your bottle, and for how long? If your tube was 150feet long a the system will have a resonant period of about 45 seconds (assuming that there is no damping, which would make this period longer), so to definitely see any effect you would have had to wait at least this long.

What you describe in your 'tubular experiments' sounds entirely reasonable to me and exactly what I would expect to happen from standard physics, but I don't see how it would apply to a tree.

Although you get a downward flow of sugars through the Phloem and an upward flow through the Xylem, as you mentioned earlier, 98% of the water that is lifted up is evapourated, so the less than 2% of water going down would have to lift 20 times that amount of water. For the syphon device you describe in the link to work the weight on the downward side must be greater than the upward side or it obviously won't work. Unless the density of the sugar solution is 50 times that of the water coming up I don't see how this could work.

btw. You came to a hands on science event I was running in Brixham a couple of years ago.

You had at in the experiment a loop of tube filled with water with a height difference from the top to the bottom of more than 10m? So you have prooved that a column of water more than 10m high is stable, so why shouldn't a xylem be able to do the same thing? Especially as it has had 200million years to optmise this process.

*****AnswerA little more than 10 metres actually, 24 metres to be exact, as that was the length of tube I was using at the time.

The column of water is not stable in the tubes, cavitations is demonstrated as the stress on the water bead causes bubbles to form and the columns collapse eventually, just as they do in the tree.*****

You are right what you were doing (injecting denser fluid near the top of the tube on one arm of a syphon loop) is not conventional syphoning, you are making one arm of the syphon heavier by using a higher density fluid rather than by using a lengthened arm, but if this works then a syphon will work.

*****AnswerFeel free to try your siphon at these heights. Ill bet you draw the same conclusion that many others have already observed as the accepted height at which a siphon will work.

Picture a loop of tubing suspended above the 10 metre limit, producing an unbroken bead of water, under the tension produced by the equal weight of the water on both sides of the tubes. Now initiate the lowering of one of the ground based bottles to try to cause a siphon. The result would be that the lowering of the one bottle would merely cause the bead of water to become elasticised and stretch to the point where it would collapse. But during the stretching process, we hypothetically inject a tiny amount of concentrated saline solution coloured, in one side of the loop at the top/upper most part of the loop. The result would be an obvious independent flow and return system, within the pre tensioned bead of water, flowing with total disregard to pressures, and creating its own pressure changes within the tension placed upon the bead of water.This flow system does not require pressure in order to function, but delivers pressures as it functions. *****

If the water column has not cavitated there is no reason why it shouldn't syphon - the reason why it is often said that you can't syphon over 34 feet is that the fluid will have a tendancy to cavitate. How far did you lower your bottle, and for how long? If your tube was 150feet long a the system will have a resonant period of about 45 seconds (assuming that there is no damping, which would make this period longer), so to definitely see any effect you would have had to wait at least this long.

*****AnswerWrong, there is a fundamental reason why siphon does not occur as explained above.

The bottle was lowered 2 steps, presumably around half a metre, as I did not measure the steps, and remained for well over your 45 seconds without any evidence of siphon.

What you describe in your 'tubular experiments' sounds entirely reasonable to me and exactly what I would expect to happen from standard physics, but I don't see how it would apply to a tree.*****AnswerAccording to the points you raise above, this is not quite correct, as your understanding of the siphon does not apply here. *****

Although you get a downward flow of sugars through the Phloem and an upward flow through the Xylem, as you mentioned earlier, 98% of the water that is lifted up is evapourated, so the less than 2% of water going down would have to lift 20 times that amount of water.

*****AnswerThis paradigm can lift many thousands of times the volume going up, and only requires a minute of solutes flowing down to cause the greater volume of less dense solution to flow up, giving the tree more than enough water to evaporate and produce a denser sap.*****For the syphon device you describe in the link to work the weight on the downward side must be greater than the upward side or it obviously won't work. Unless the density of the sugar solution is 50 times that of the water coming up I don't see how this could work. *****AnswerThis is where you go wrong David: imagine a 24 mil bore tube on one side and a 6 mil bore tube on the other side, blended seamlessly together to form a single looped open ended tube of different sizes immersed at equal levels in two bottles of water, suspended 24 metres vertically by the centre. The weight of the 24 mil bore side of the loop will be counterbalanced exactly by the 6 mil bore side of the tube, with no net movement either way. Now add the tiny amount of salt to the 6 mil bore side at the centre and circulation begins. In the case of the tree, the structure and size differences of the tubes compensates for the loss of moisture through the leaves and returns the resulting concentrates back towards the ground.

btw. You came to a hands on science event I was running in Brixham a couple of years ago.

I do remember popping in the town hall now you mention it, as you were closing your event I believe.

Thank you for remembering me.

Andrew

Death is natures way of telling us to slow down.

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quote:imagine a 24 mil bore tube on one side and a 6 mil bore tube on the other side, blended seamlessly together to form a single looped open ended tube of different sizes immersed at equal levels in two bottles of water, suspended 24 metres vertically by the centre. The weight of the 24 mil bore side of the loop will be counterbalanced exactly by the 6 mil bore side of the tube, with no net movement either way. Now add the tiny amount of salt to the 6 mil bore side at the centre and circulation begins.

This system will produce a flow, but because the amount of water in the system is allways the same, if you get 1 litre falling out of the 6mil tube, the 24mil tube will suck up 1 litre, however because the area of the bigger tube is 16 times larger the water you have sucked up will only go up 1/16th of the tube, you haven't pumped any water to the top.

quote: In the case of the tree, the structure and size differences of the tubes compensates for the loss of moisture through the leaves and returns the resulting concentrates back towards the ground.

But how are you getting the water out at the top? The water is at a negative pressure, this means that to get it out you have to pull, and pull very hard against a large pressure. Evaporation will do this, but if evapouration is doing the work you don't need the tube coming down and that is just the conventional model you are so dead set against.

In what way has your system produced a net flow of water to the top of the cliff? Overall you have moved water from one jar to another one next to it. If you had filled a bowl of water at the top of the cliff that would be equivalent to what the tree is doing, and I will belive it could be an issue when you can do that.

quote:Picture a loop of tubing suspended above the 10 metre limit, producing an unbroken bead of water, under the tension produced by the equal weight of the water on both sides of the tubes. Now initiate the lowering of one of the ground based bottles to try to cause a siphon. The result would be that the lowering of the one bottle would merely cause the bead of water to become elasticised and stretch to the point where it would collapse. But during the stretching process, we hypothetically inject a tiny amount of concentrated saline solution coloured, in one side of the loop at the top/upper most part of the loop. The result would be an obvious independent flow and return system, within the pre tensioned bead of water, flowing with total disregard to pressures, and creating its own pressure changes within the tension placed upon the bead of water.

So would it break if you lift one of the jars, which will reduce the tension in the water column...?

Yes David, cavitation will inevitably cause the columns to collapse. The additional tension placed upon the bead by lowering the level of one side, merely serves to hasten the process of cavitation. Even if you raise a jar following initial lowering, the cavitation is already underway. In the link that Rosy put on her post, I have tried to address the way cavitations continually form and self repair within the multi conduit system of a tree. Cavitations do not interfere/interrupt the flow within the narrow tubes of the bench top model. In fact, the cavitations/bubbles behave oddly when sufficient saline solution is added. They are observed to flow down instead of up, and there is water flowing around the bubbles also.

Fascinating to see bubbles flowing down instead of up. Maybe you might want to test the simple bench top version for yourself?

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But there is no difference in the pressure of the water at the top of the tube, between your clifftop experiment and an equivalent syphon, so I don't see why you think one will work and the other won't. What sized tube did you use for your experiments?

Yes! Altering the heights of the 2 jars merely serves to place additional stress on the fluids within the unbroken bead of water. Therefore, the collumn is not permanently stable, as is so in the tree and plant. The tree gets around this problem by having an outer sleeve (bark) and a multi conduit system inside the outer sleeve. This enables the resulting pressure change when cavitation occurs, to gain height due to the resulting downward force on the broken bead, pushing up fluid under greater force to refil the broken bead.

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This system will produce a flow, but because the amount of water in the system is allways the same, if you get 1 litre falling out of the 6mil tube, the 24mil tube will suck up 1 litre, however because the area of the bigger tube is 16 times larger the water you have sucked up will only go up 1/16th of the tube, you haven't pumped any water to the top.

The model is simple, I do not have the time nor the inclination to try to construct a perfect artificial tree.

I only have to show the driving force in this paper. The trees design takes care of evaporation as the water and minerals flow though its veins

quote: In the case of the tree, the structure and size differences of the tubes compensates for the loss of moisture through the leaves and returns the resulting concentrates back towards the ground.

But how are you getting the water out at the top? The water is at a negative pressure, this means that to get it out you have to pull, and pull very hard against a large pressure. Evaporation will do this, but if evapouration is doing the work you don't need the tube coming down and that is just the conventional model you are so dead set against.

Common sense should tell anyone that there is no attempt to extract water from the tubular models

In what way has your system produced a net flow of water to the top of the cliff? Overall you have moved water from one jar to another one next to it. If you had filled a bowl of water at the top of the cliff that would be equivalent to what the tree is doing, and I will belive it could be an issue when you can do that.

I have never seen a bowl of water at the top of any tree other than those left by the owners of apple trees to prevent scrumpers.

In the case of a tree, we could place a plastic bag over a branch and collect and extract the condensed water in its canopy.

It is possible to design a model that can lift sea water, extract pure water and return the denser ballast to the sea through a tube in order to provide the pumping for the desalination. But I have long since given up jumping though loops to amuse people.

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but if evaporation is doing the work you don't need the tube coming down and that is just the conventional model you are so dead set against. [quote/]

Evaporation is doing the work. But not in the way it has been erroneously interpreted by Dave et al. I am perplexed that you have stated that there is no downward flow in trees?

From an earlier post in case you missed it:Transport of salts

The liquid which travels in the xylem is not, in fact pure water. It is a very dilute solution, containing from 0.1to1.0% dissolved solids, mostly amino acids, other organic acids and mineral salts. The organic acids are made in the roots; the mineral salts come from the soil. The faster the flow in the transpiration stream, the more dilute is the xylem sap. Experimental evidence suggests that salts are carried from the soil to the leaves mainly in the xylem vessels.

The xylem sap is always a very dilute solution, but the Phloem sap may contain up to 25 per cent of dissolved solids, The bulk of which consists of sucrose and amino acids.

There is a good deal of evidence to support the view that sucrose amino acids and may other substances are transported in the phloem. The movement of water and salts in the xylem is always upwards, from the soil to the leaf. But in the phloem the sap may be travelling up or down the stem. The carbohydrates made in the leaf during photosynthesis are converted to sucrose and carried out of the leaf to the stem. From here the sucrose may pass upwards to growing buds and fruits or downwards to the roots and storage organs. All parts of a plant which cannot photosynthesise will need a supply of nutrients bought by the phloem. It is possible for substances to be travelling upwards and downwards at the same time in the phloem.

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Hm, I'm not at all convinced.Transport of sugars between living cells (such as in the phloem) actually requires the input of energy. Sugars use ATP (the cellular energy transfer compund) to move sugar (and amin acid, and any charged or bulky species) molecules across cell membranes, including across the boundaries between seive plates.I simply can't see how this is compatible with the idea that the gravitational potential of the more concentrated solution is lifting the water up the xylem.

quote:It is possible to design a model that can lift sea water, extract pure water and return the denser ballast to the sea through a tube in order to provide the pumping for the desalination. But I have long since given up jumping though loops to amuse people.

I can't imagine how... no need to design a system, but would you like to outline the general principles...?

Rosy, please repeat the simple experiments and understand the driving forces of nature.

If you cant get hold of the tubes, joints and syringe body, let me post them to you.

1. It is an impossibility of the highest degree for evaporation to take place from a liquid containing solutes of salt and sugars, without concentrating said solutes.

2. It is a function of gravity to act upon said solutes when they occur at an elevated point above less concentrated solutes. (see Atlantic conveyor system)

3. For every action there is a reaction. Any downward flow will cause an inevitable upward flow!

4. The experiments have been demonstrated at Primary level education, in schools. At secondary schools, at Universities, at Derriford Hospital’s Physics Department in Plymouth. At the London International Inventions Fair in 1997, witnessed by some 3 thousand visitors and inventors. On Westcountry Television News, BBC Radio in Paignton, and has not yet failed to convince all who have witnessed its efficacy in delivering the flow rates observed in plants and trees!

Now why can’t you understand the simplicity of this discovery and its many applications?

Nevertheless, I am grateful for all of the replies on this thread and thank you for your input

Andrew

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I know how the experiment works. That's not my question.It's quite obvious from your description how the weight of the solution pulls the (lighter) water over the top of the tubing.But at the top of the loop, as in a conventional siphon, the water is at much less than atmospheric pressure (it has to be as there's a force holding up the column of water below) so I don't see how you propose that the water gets out of the xylae into the leaves (essentially the question Dave put further up the thread).

You haven't explained to me how your proposed system for lifting sea-water works.

The following review came from a letter I wrote to professor H T Hammel,who is member of the Max Plank Institute.

Within a 2 weeks I received his reply

INDIANA UNIVERSITY

SCHOOL OF MEDIICINE date September 6/ 1995

Dear Mr Fletcher:

I received the information you sent me regarding your ideas about fluidtransport in trees, in tubing and in the vascular system in humans.

I will study your ideas and comment upon them as soon as possible. A Quickscan of your Brixham experiment prompts me to ask if you conducted thisexperiment with boiled water without any solute added to the tubing oneither side of the central point which you raise 24 meters? I expect thatyou could raise the tubing to the same height with or without solute in thewater. In any case , your experiment confirms that clean water (water thatis unbroken water, water that is without a single minute bubble of vapour)can support tension of several hundreds of atmospheres. The record tensionobtained experimentally is 270 atmospheres. At 10 degrees C. (c.f. Briggs,L. Limiting negative pressure of water. Journal of Applied Physics 21:721-722 1950).

I expect even this tension at brake point can be exceeded by carefulcleansing of the water, to remove even the most minute region of gas phase.When the water is already broken, as occurs when gas is entrapped onparticulate matter in ordinary water, the water will expand around even asingle break when tension (negative Pressure) is applied to the water. Whenyou boil the water, prior to applying (2.4-1) ATM negative pressure to thewater in the highest point of the tubing, you eliminate some of these breaksin ordinary water. I expect that dissolving NaCl or other solutes in thewater will have little or no effect on the way you measure the tensilestrength of water.

I am enclosing some reprints that may interest you. Some of these deal withnegative pressures we have measured in tall trees, mangroves and desertshrubs. Other reprints deal with how solutes alter water in aqueoussolutions and how colloidal solutes (proteins) affect the flux of proteinfree fluid between plasma in capillaries and interstitial fluid.

Sincerely H.T. Hammel Ph.D.

Death is natures way of telling us to slow down.

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